Homosexuality in the Animal kingdom

Pleasure ride: A male killer whale rides the dorsal fin of another male. Sex just for the pleasure of it is common in many animals. Photo: Brian Scott. Original photo obtainable from http://www.brianorca.com/brianweb/. REF: picture no PIC00166.jpg

Can animals be homosexual?

The sexual urge is strong in all animals. Many species have sex outside the mating season and commonly enjoy sex without reproductive intent – rubbing their sexual organs against each other or stimulating themselves or their partners in other ways. When animals of the same gender have sex, they exhibit homosexual behaviour. We call such animals homosexuals. Some animals are consistently homosexual throughout their life.

Two homosexual male shelducks, Tadorna tadorna, mating. While homosexuality probably occurs across the whole Animal Kingdom, the animals dominating the statistics are the larger, more conspicuous species, especially those where the male and female differ greatly, making same-sex mating easy to spot. Foto: Scanpix. Origial photo obtainable from www.scanpix.com/

Which animals are homosexual?

The earliest known mention of animal homosexuality is found in a 2300 year old description of hyenas by Aristotle. Hyena clitoris and labia look like a penis and scrotum, and this made him believe all hyenas are male. Sex between the females is not uncommon, so Aristotle was right in describing them as homosexuals, only they where lesbians rather than gays! Detail of painting by Rafael.

Homosexuality has been observed in most vertebrate groups, and also among insects, spiders, crustaceans, octopi and parasitic worms. The phenomenon has been reported in more than 1500 animal species, and is well documented for 500 of them, but the real extent is probably much higher.

The frequency of homosexuality varies from species to species. In some species, homosexuality has never been reported, while in others the entire species is bisexual. In zoos around 1 in 5 pairs of king penguins are of the same sex. The record is held by orange fronted parakeets, where roughly half of all pairs in captivity are of the same sex.

Why haven’t we been told?

Homosexuality in animals has been known since Antiquity, but has only recently made it into mainstream science. The cause may be a lack of interest, distaste, fear of ridicule, or scientists fearing to lose their grants. The few scientists publishing papers on the topic, often made sure their own sexual preferences were known, directly or indirectly.

Some scientists have interpreted same-sex pairing as anything but sex. In a study of giraffes in Africa a researcher registered all cases where a male sniffed a female as “sexual interest” – while anal intercourse with ejaculation between males was registered as a form of ritualised fighting (“sparring”), despite the fact that 94% of all registered sexual activity in one area took place between males. Only recently has scientists started investigating homosexuality in animals in earnest.